top of page

Metal Reactivity and Replacment Reactions

Lizzy Choi

Almaty International School


The following experiment was conducted to illustrate the concept of metal reactivity and replacement reactions.

Summary of Procedure

  • Flask filled with water, hydrochloric acid, and copper chloride

  • Aluminum foil balls are added

  • Hydrochloric acid (HCl) removes (Al) Oxide layer (coating) to proceed reaction

  • Aluminum displaces copper (Cu) from copper chloride (CuCl2) due to higher reactivity

  • Hydrochloric acid (HCl) reacts with Aluminum

  • Hydrogen gas produced to ignite light

  • Copper causes green/blue flame to appear

Figure 1. Image of chemical reaction

The experiment described involves a series of chemical reactions between aluminum (Al), copper(II) chloride (CuCl₂), and hydrochloric acid (HCl). Here's the step-by-step breakdown of the reactions and the corresponding chemical equations:

1. Initial Reaction: Removal of Aluminum Oxide Layer

Initially, aluminum foil, which typically has a thin layer of aluminum oxide on its surface, is placed in a flask containing hydrochloric acid (HCl). The hydrochloric acid reacts with the aluminum oxide, removing it and exposing the clean aluminum metal underneath. This step is necessary because aluminum oxide acts as a protective layer, hindering further reactions.

Al2O3 + 6HCl → 2AlCl3 + 3H2O

2. Displacement Reaction: Aluminum Reacts with Copper(II) Chloride

Once the aluminum oxide layer is removed, aluminum metal reacts with copper(II) chloride solution. In this displacement reaction, aluminum replaces copper in the compound because aluminum is more reactive than copper. As a result, copper metal precipitates out of the solution, while aluminum chloride forms.

2Al + 3CuCl2 → 2AlCl3 + 3Cu

3. Reaction of Aluminum with Hydrochloric Acid

Simultaneously, the aluminum metal also reacts with the hydrochloric acid present in the solution. This reaction produces aluminum chloride and hydrogen gas.

2Al + 6HCl → 2AlCl3 + 3H2

4. Ignition of Hydrogen Gas

The hydrogen gas produced in the reaction with hydrochloric acid can be collected and ignited. When ignited, hydrogen gas combusts, reacting with oxygen in the air to form water vapor. This combustion process releases energy, resulting in a flame. Additionally, the presence of copper in the flame can impart a characteristic green or blue color due to the emission spectrum of copper ions when heated.

2H2 + O2 → 2H2O (combustion reaction of hydrogen gas)

To summarize the overall chemical reactions involved in this experiment:

Al2O3 + 6HCl → 2AlCl3 + 3H2O

2Al + 3CuCl2 → 2AlCl3 + 3Cu

2Al + 6HCl → 2AlCl3 + 3H2

2H2 + O2 → 2H2O (combustion reaction of hydrogen gas)

Overall, this experiment demonstrates several fundamental concepts in chemistry, including displacement reactions, acid-metal reactions, and combustion reactions. It also showcases the characteristic flame color produced by certain metals when heated.


bottom of page